a) Field of the Invention
The present invention relates to a damper which actuates gate plates such as baffles for cold air inlets using a motor as a driving source. It specifically relates to a damper suited to control cold air distribution in a refrigerator.
b) Description of the Related Art
A conventional damper is disclosed in, for example, Japanese patent laid open H6-109354 or U.S. Pat. No. 5,398,910. (See FIG. 24.)
The damper 70 of the structure is used in a refrigerator 80 as illustrated in FIG. 25. The refrigerator 80 is divided into a freezer 81 and a refrigeration chamber 82 and an evaporator 84 is arranged at the bottom of the freezer 81. A fan motor 85 is arranged behind the evaporator 84 to circulate cold air obtained at the evaporator 84 through the freezer 81 and the refrigeration chamber 82. A partition 86 is provided between the evaporator 84 and the refrigeration chamber 82, which prevents cold air in the evaporator 84 from flowing directly into the refrigerating chamber 82. Cold air passage 87 is provided between the back of the partition 86 and the inner wall of the refrigerator 80.
In the motor damper 70, a baffle 72 and a driving mechanism 73 including a synchronous motor etc. are arranged putting the pivot, the rotation center, for the baffle 72 therebetween. The drive mechanism 73 transforms the rotational torque of the synchronous motor and puts out a force in the thrust direction, using a rack and pinion mechanism, to rotate the baffle 72 around the pivot 71 to open/close the baffle 72. To control temperature in the refrigerator, cold air is shut completely when the baffle 72 is closed, it flows into each of the chambers when the baffle 72 is opened.
In the aforementioned motor damper 70, the torque in the rotational direction is transmitted as torque in the thrust direction. When considering the manufacturing accuracy each component must have, the engagement of the baffle 72 or the members in the driving mechanism 73 need to have some tolerance. On the other hand, to control temperatures accurately, cold air must be shut completely when the baffle 72 is closed.
Therefore, in the motor damper 70, in order to better seal the space between the baffle 72 and the frame 74 to close the cold air inlet 76 with the baffle 72 completely, a plate spring (not illustrated) is provided to press the baffle 72 in the same direction. In addition, the contact surface of the baffle 72 and the frame 74 is sealed with a soft tape 75 to hold the frame 74.
In the structure, the plate spring pressure is strong enough to shut cold air completely; however, the pressure from the plate spring varies depending on the open-close position of the baffle 72; it is not preferable to operate the drive mechanism 73 such as a synchronous motor against this pressure.
In addition, because the motor damper uses the rack and pinion structure, the baffle 72 does not open to the position parallel to the cold air flow; it opens to the lower position as shown in FIG. 25. Therefore, even if the baffle 72 is open, it impedes cold air flow; this is unfavorable for diffusing cold air rapidly. Moreover, the angle by which the baffle 72 opens tends to become even smaller due to warping of the plate spring.
Furthermore, the rack and pinion mechanism requires wider than normal width N in the driving mechanism 73, occupying a large dead space therein.
Recently, popular refrigerators have separate chambers such as a refrigeration chamber, a freezer, a vegetable crisp in which temperatures are controlled for each of the chambers separately; or they have a large chamber in which temperatures are controlled for each of the upper and lower sections separately. In these types of refrigerators, cold air passages 87 are provided exclusively for each of the chambers or sections to control the amount of cold air which flows into each of the chambers.
To accomplish the task, some refrigerators use a plurality of apparatus such as the motor damper 70 as shown in FIG. 24; some refrigerators use a double damper 77 having two hollow sections shown in FIG. 26.
In the aforementioned double damper 77, two hollow sections 76a, 76b are formed on the frame 74; the drive mechanism 73 including a motor etc. is arranged at the back bottom. Baffles 72a, 72b, which are the same as those used in the motor damper 70, are arranged for each of the inlets; each of the baffles 72a, 72b controls cold air for each of the cold air passages 87, 87 independently.
These baffles 72a, 72b are driven by one synchronous motor (not illustrated) in the drive mechanism 73 and operate in the following four modes:
both baffles 72a, 72b are open; PA1 both baffles 72a, 72b are closed; PA1 the baffle 72a is open and 72b is closed; or PA1 the baffle 72a is closed and 72b is open.
The double damper 77 obtains output from the synchronous motor via a rack and pinion to move the baffles 72a, 72b arranged above the driving mechanism 73 independently. This increases the size of the driving mechanism 73 including the synchronous motor, rack and pinion mechanism, etc. Particularly in this structure, the rack is abutted to the pivotal side of the center portion of the baffle 72a, 72b, the distance R between the racks becomes large; this increases the size of the driving mechanism 73.
On the other hand in order to decrease the size of the driving mechanism, the distance between both of the hollow sections 76a, 76b must be small. A small distance P between both of the hollow sections 76a, 76b provides insufficient heat insulation for the space between the cold air passages 87 which communicate with two cold air inlets 76, 76: change in temperature in one of the cold air passage 87 affects the temperature of the other cold air passage 87. This makes it difficult to accurately control temperature for each of the chambers.
Some popular dampers uses a motor such as a DC motor or stepping motor, not a synchronous motor, as a driving source. Many of these motors do not use a position sensor which increases cost but control parameters such as the active time or the number of pulses for opening and closing the baffle. However, in these types of dampers, the baffle may stop operating for a moment if the stepping motor fails to synchronize or if the baffle is frozen; the baffles may not be able to operate accurately. They may, for example, leak cold air because the baffle is not closed perfectly.